Madjid Mohseni

Professor

Research Classification

Drinking Water
Chemical Pollutants
Used Water
Clean Technologies

Research Interests

Drinking water quality and treatment
Advanced oxidation
UV based water purification and treatment
Water re-use
Electrochemical water treatment processes

Relevant Degree Programs

 

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Master's students
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Postdoctoral Fellows

Graduate Student Supervision

Doctoral Student Supervision (Jan 2008 - Mar 2019)
Application of ultraviolet light-emitting diodes (UV-LEDs) for water disinfection by multiple wavelengths and pulsed irradiation (2018)

No abstract available.

Surfactant surface chemistry and heparin-based anticoagulant drug design studied by molecular dynamics simulation
 (2018)

This dissertation uses molecular dynamics (MD) simulations to mainly focus on the study of the interaction between neutral surfactants-water and anionic surfactant-anionic polyelectrolyte on the water surface. Besides, this study devotes to finding the possible routes of improving the design of a drug candidate, polyethylene-glycol-linked cationic binding groups (PEG)n-HBG, to inhibit polyphosphate (polyP) thrombotic activities. It is found that the behavior of the nonionic polyoxyethylene glycol alkyl ether on the water surface is more anionic-like, even though the surfactant is overall neutral. The non-ionic surfactant increases the depth of the surface anisotropic layer and the average number of hydrogen bonds per water molecule. MD simulation showed that the negatively-charged O atoms have the most impact on the orientation of water as most water molecules arrange with their H atoms pointing toward the surface. In contrast, the behavior of the zwitterionic surfactant, N-dodecyl-N, N-dimethyl-3-ammonio-1-propanesulfonate, on the water surface is more cationic-like as the positively charged group is more capable of orienting interfacial water. The zwitterionic surfactant orients water molecules with their OHs mostly pointing toward the liquid water. While the complex formation between highly-charged surfactants and polyelectrolytes of the same charge is generally expected to be prohibited by the electrostatic repulsion, my study shows it is possible to form thermodynamically stable complexes in the presence of excess ions. With excess Na⁺ ions, the charge screening effect allows anionic polyelectrolyte to weakly interact with anionic surfactant via hydrogen bonds. In the presence of divalent Ca²⁺ ions, the surfactant and the polymer is strongly coupled by forming Ca²⁺ ion bridges and hydrogen bonds.The mechanism of complex formation between (PEG)n-HBG and polyP are studied using metadynamics simulations with the all-atom and coarse-grained force fields. It is shown that the PEG length does not have any impact on the interaction between the (PEG)n-HBG and polyP. However, it mostly improves the drug’s hemocompatibility by preventing the cationic drug from binding to other negatively- charged biomolecules. Increasing the number of the positive charges on the headgroup strengthens drug binding to polyP. It is found that the binding of (PEG)n-HBG remains intact against various lengths of polyP.

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The impact of natural organic matter (NOM) on photocatalytic process for the degradation of micropollutants (2017)

Photocatalytic oxidation process has been demonstrated as an effective technology for the removal of micropollutants in water. This process, however, is greatly affected by the presence of natural organic matter (NOM) in natural water, which interferes with treatment process by absorbing UV radiation and scavenging oxidant species. This research focused on investigating the effect of NOM on the photocatalytic oxidation of 2,4-dichlorophenoxy acetic acid (2,4-D), as target contaminant at different pH. Experiments were performed in fluidized photocatalytic reactor using template free photocatalyst spheres.Changes in solution pH were used to decouple the effects of NOM on adsorption and major oxidative mechanisms, e.g., reactions on the surface of the photocatalytic spheres via positive hole mediation and in the solution via hydroxyl radicals (●OH) reaction. At pH 3, due to electrostatic attraction between solutes (2,4-D and NOM) and photocatalyst surface, photocatalytic oxidation mostly occurred via charge transfer on the surface of the photocatalyst. At pH 7, on the other hand, electrostatic repulsion between solutes and photocatalyst surface reduced adsorption and the process was primarily driven by hydroxyl radical reactions. The removal of 2,4-D reduced from 49% in the absence of NOM to 7% in the presence of 5 mgL-1 TOC NOM in neutral pH. At pH 3, this reduction was from 88% to 58%. It was observed that at neutral pH, due to higher aromatic moieties concentration and lower NOM adsorption, the effect of NOM on scavenging ●OH was considerable. This effect substantially decreased at low pH due to high adsorption of NOM.Higher 2,4-D removal at low pH was also due to the effect of pH on the kinetic of photocatalytic oxidation. Photocatalytic oxidation at pH 7 followed first order kinetic model. At pH 3, on the other hand, the rate of oxidation was a combination of first order and L-H models. Furthermore, the dependence of rate constants on UV intensity changed with pH; the rate constant was directly proportional to UV intensity at pH 3; whereas it is proportional to the square root of intensity at pH 7.

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The removal mechanism of natural organic matter by ion exchange resins from thermodynamic perspectives (2017)

Natural organic matter (NOM), a constituent in surface drinking water sources, requires removal to minimize its negative impacts on water quality and water treatment processes. Ion exchange (IEX) has been considered as an effective technology for the removal of NOM. However, despite many studies on the IEX removal of NOM, the removal mechanism and the molecular interactions involved in the IEX process are quite unknown due to the complexity of the NOM molecular structure. This research aimed to investigate the NOM removal with a focus on fundamentals underpinning the IEX process and the molecular interactions/forces that drive the retention of NOM onto the IEX resins. Different isolates of NOM along with some pure organic acids were studied. Hydrophobicity was found to play a key role in the removal process. The changes that the hydrophobic moieties impose to the structure of water molecules (i.e., entropy reduction) were found very influential in determining the selectivity of the IEX process. Moreover, the removal of UV-absorbing compounds (more hydrophobic fraction of NOM) was enhanced in the presence of sodium sulphate, as the electrostatic interactions are screened by added salt and consequently the entropic contribution to the removal is promoted. Nonetheless, the entropic contribution from the resin phase (i.e., hydrophobic resin backbone) was shown to negatively impact the removal of UV-absorbing compounds. Overall, combining the findings, it is concluded that the difference in the hydrophobicity (entropy) of the water and the resin phase is the main driving force in transferring NOM molecules from water to the resin. The contribution of the electrostatic and hydrophobic effects to the removal of NOM by IEX resins was further evaluated by quantitative characterization of the thermodynamic properties using isothermal titration calorimetry technique. The results confirmed the significance of entropic contribution to the removal of components with higher hydrophobic characteristics.Findings of this research provide a quantitative framework for the interpretation of the experimental results and facilitate the proper design of the IEX process for different water sources and under various conditions.

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The use of 185 nm radiation for drinking water treatment (2017)

The treatment of water via 185 nm radiation allows for the oxidative degradation of trace organic contaminants without the need for chemical addition.Critical information required for the practical application of such a processhas been lacking. Carbamazepine was determined to be an ideal probe compound for study of the 185 nm regime due to negligible direct photolysis at254 nm. An increase in probe degradation rate due to 185 nm is observedwith increasing temperature when water is the only significant absorber ofphotons. A comparison with the temperature dependence of the 254 nm -H₂O₂ process is made and a fundamental explanation proposed. Experimental evidence reveals that probe degradation rate is strongly influencedby anionic composition at environmentally relevant concentrations, particularly chloride. Evidence for the role of the chlorine radical is obtained bykinetic studies involving select probes, radical scavengers, and ionic strength.Interactions between the major organic and inorganic solutes indicate thatresulting degradation kinetics are highly sensitive to the composition of thewater matrix, a fact that has been neglected from the literature. A methodto quantify molar absorption coefficients is developed that is not prone toerrors due to stray radiant energy or wavelength inaccuracies. A method toquantify the 185:254 nm output of a low pressure mercury lamp is presentedwith results in agreement with values reported in the literature. In additionto the hydroxyl radical (*OH), other radical species such as chlorine (C1*) and sulphate (SO₄*¯) are proposed to be involved in oxidative degradationof trace organics in the 185 nm regime. This suggests that the degradation rate of a given target contaminant depends on the composition of the water matrix, the second-order rate constants with the relevant radicals, and the relative reaction rate constants of the target and the matrix.

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Assimilable organic carbon formation during ultraviolet-hydrogen peroxide advanced oxidation treatment of surface water (2016)

No abstract available.

Computer-aided study of Vacuum-UV/UV process for removal of organic pollutants from water supplies (2016)

Water authorities are increasingly worried about the occurrence of organic micropollutants (e.g., algal toxins, endocrine disrupting compounds, pesticides, industrial chemicals, taste and odor compounds) in water supplies. Removal of organic micropollutants (OMPs) from water is cost-prohibitive, particularly for small and remote communities. Vacuum-UV/UV process, an incipient catalyst/chemical-free advanced oxidation process (AOP), is potentially a cost-effective solution for removal of harmful micropollutants from water. The main objective of this thesis was to investigate the feasibility of VUV/UV process for the removal of OMPs using a comprehensive computational fluid dynamics (CFD) analyzes. The developed model involved simultaneous resolution of the local transfer equations of momentum, mass, and radiative energy (for UV and VUV radiations), along with a complex kinetic scheme with more than 50 reactions. Given the importance of 185 nm and 254 nm emissions for the accurate modeling of the VUV/UV process, a new experimental method for measuring VUV and UV emissions of the mercury lamps was proposed. To assess the CFD model, VUV-induced degradation of model pollutants (atrazine, p-CBA) in ultrapure water samples was investigated under laminar flow conditions utilizing an axisymmetric laboratory-scale reactor. Afterwards, using an asymmetrical pilot-scale VUV/UV reactor, experimental validation of the CFD model was conducted for simulating the degradation of model pollutants (atrazine, 1,4-dioxane) in synthetic and natural contaminated waters under turbulent flow regime. Comparison of the modeling and experimental data indicated that the developed CFD model was able to predict successfully the degradation rate of target pollutants in the analyzed reactors. In addition, the proposed model showed to predict well the impact of the flow rates, and water matrix (NOM and alkalinity) on target pollutants degradation with less than 3 % average absolute relative deviation (AARD%). Relying on the insights gained by CFD analysis (e.g., knowing the critical role of pollutant mass transfer on the AOP performance of VUV systems), an improved VUV/UV process was developed through retrofitting baffles within the reactor. When compared the pollutant degradation and energy consumption of VUV/UV and H₂O₂/UV processes, superior performance of the improved VUV/UV process was observed.

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Effect of water matrix on Vacuum UV process for the removal of organic micropollutants in surface water (2015)

UV-based advanced oxidation processes (UV-AOPs) have been demonstrated as effective technologiesfor the removal of micropollutants in water. One promising UV-AOP is Vacuum UV (VUV), which relies on the formation of hydroxyl radicals (HO•) by the photolysis of water induced by VUV photons. TiO₂/UV photocatalysis is another promising AOP. Both VUV and UV photocatalysis are greatly affected by the water matrix, inorganic ions and natural organic matter (NOM). Water constituents can absorb the UV and VUV radiations, they can act as HO• radicals scavengers, and can produce radicals when photolyzed.The main objective of this research was to study the effects of water matrix on the efficiencyof VUV for the degradation of micropollutants (with atrazine as a model contaminant). First, theabsorbance of radiation at 254 nm and 185 nm was measured in the presence of different ionsand NOM. All the inorganic ions showed a molar absorption coefficient equal to zero at 254 nmexcept nitrate with a ɛ= 3.51 M−¹ cm−¹. On the other hand, at 185 nm all the ions absorbed185 nm radiation, with chloride showing the highest absorption coefficient ɛ=2791 M−¹ cm−¹.NOM showed a high absorption coefficient at both 254 and 185 nm ranging from 116 to 638 M−¹cm−¹ at 254 and from 1137 to 1537 M−¹ cm−¹ at 185 nm). Second, the HO• scavenging effectsof different components were evaluated; nitrate showed a detrimental effect both with UV/H₂O₂and with VUV. The presence of 50 ppm of bicarbonate reduced the degradation rate of atrazineconsiderably. Sulfate seemed to photolyze at 185 nm to form HO•. NOM was found to be a strongHO• scavenger : in the presence of 9 ppm (DOC) NOM, less than 1% of the HO radicals were available to react with atrazine. The next component of this work involved developing a method for the measurement of quantum yield of atrazine at 185 nm. This allowed to measure the degradation of atrazine due to photolysis only. Finally, this research investigated the combination of VUV with TiO₂/UV. The results showed that incorporating photocatalysis cannot improve significantly theefficacy of VUV.

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Evaluations of conventional, slow sand filtration, ozone, ozone/H2O2 and UV/H2O2 treatments for decontamination of the selected PPCPs and EDCs and their effect on THMs formation potential (2014)

Pharmaceuticals, personal care products (PPCPs), endocrine disrupting compounds (EDCs), and disinfectant by-products (DBPs) in drinking water are all associated with potential health implications that warrant their removal and formation prevention during drinking water treatment. This work presents the results of several pilot scale studies carried out using; a) dual train conventional treatment processes of coagulation, flocculation, sedimentation, filtration (conventional); and b) (multistage) slow sand filtration (SSF); both coupled with ozone and advanced oxidation processes (AOPs) such as ozone/H₂O₂ and UV/H₂O₂ using natural water from three different sources. Removal of selected PPCPs and EDCs (as a group) was limited (on average 30%) by conventional treatment. On the contrary, ozone/H₂O₂ plus conventional was the most effective process (average of about 97%) to remove the selected PPCPs and EDCs, followed closely by ozone along with conventional treatment which was also very effective; however, at a slightly lower percent (average 95%) removal. Overall, ozone/H₂O₂ or ozone followed by conventional was very effective, irrespective of the raw water quality. However, the effectiveness of conventional treatment plus UV/H₂O₂ AOP was varied by raw water quality, resulting in reduced efficiency for lower raw water quality containing higher organics, bicarbonates, carbonates and particles. The average removal of PPCPs and EDCs with conventional plus UV/H₂O₂ treatment was about 86%. Experiments involving ozone or ozone/H₂O₂ followed by SSF also showed relatively high removals of target contaminants. On average, the removal rates of PPCPs and EDCs were around 95-100% for the combined processes. In comparison, stand-alone ozone or ozone/H₂O₂ showed removals of around 77% of PPCPs and EDCs. Reduction of disinfection by-products formations, measured as THM-FP (trihalomethanes formation potential), was also investigated over the course of all pilot studies and for each of the treatment scenarios. In most experiments, application of ozone/H₂O₂ and ozone alone upstream of the conventional led to additional reductions in THM-FPs as compared to that of the standalone conventional treatment. However, in most experiments, UV/H₂O₂, when applied downstream of the conventional process, increased THM-FPs of the conventionally treated water. SSF process showed to be effective and reduced 71% of THM-FPs.

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Systematic study of separators to improve the performance of passive air-breathing flat-plate microbial fuel cells (2014)

Passive air-breathing microbial fuel cells (MFC) are a promising technology for energy recovery from wastewater. The performance of the passive air breathing MFCs is dependent on the separator characteristics, isolating the anaerobic anode from the air-breathing cathode. The separator plays a more important role when the electrodes are placed in close proximity, to reduce the Ohmic resistance.The goal of the present work was to study the separator characteristics and its effect on the performance of passive air-breathing flat-plate MFCs (FPMFCs), through a combination of experimental and theoretical approaches. This was performed through characterization of 8 separators to investigate the ionic resistivity, oxygen and ethanol crossover, and proton transport number. The separators were then examined in three passive air-breathing FPMFCs with different electrode spacing, using three-dimensional graphite felt anodes and platinum-based cathodes. A numerical model was developed based on the mixed potential theory to investigate the sensitivity of the electrode potentials and the power output to the separator characteristics.The separator characterization indicated a greater susceptibility to oxygen and ethanol crossover in diaphragms, compared to the ion-exchange membranes (IEMs). Increasing the electrode spacing was also shown to be desirable for the application of diaphragms, as the anodic mixed potentials were reduced.The peak power density decreased by increasing the mass transfer coefficients of oxygen and ethanol in the separator. The model indicated that this was due to the increased mixed potentials at the anode, caused by the oxygen crossover. The mixed potentials at the cathode did not vary as the ethanol crossover increased, due to the slow kinetics of ethanol oxidation over Pt. The model also indicated that the peak power was affected by the proton transport number of the separator, which affected the cathode pH. The peak power was not sensitive to the resistivity of the separator due to the overshadowing effect of the oxygen crossover.The passive air-breathing FPMFC, using a 6 mm thick graphite felt anode, Pt-based cathode, and Nafion®117 membrane, showed the highest peak power density of ca. 0.52 W/m², which was higher than those reported for the active air flow FPMFCs in the literature.

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Reactor design parameters, in-situ speciation identification, and potential balance modeling for natural organic matter removal by electrocoagulation (2013)

Electrocoagulation (EC), a disruptive “green” technology, was investigated for the removal of natural organic matter (NOM) from drinking water sources. Three anode materials (aluminum, zinc, and iron) and three NOM sources (Suwannee, Nordic, and a local source) were investigated. After one minute of process time, dissolved organic carbon (DOC) reduction was approximately 70-80%. High performance size exclusion chromatography (HPSEC) fractionation showed reductions mostly in the larger apparent molecular weight (AMW) fraction of NOM, from 76% of NOM > 1450 Da initially to approximately 40% after EC. For iron EC, significant EC design variables were investigated, including: current density (i) (2.43-26.8 mA/cm²), and charge loading rate (CLR) (100 to 1000 C/L/min). Optimum NOM removal was found at i ~10 mA/cm² and lower CLR. In-situ identification of iron speciation in EC investigated the impact of i and CLR on speciation and NOM removal from a local natural source. Low i and intermediate CLR increased bulk pH and reduced bulk dissolved oxygen (DO), where green rust (GR) was identified in-situ for the first time in EC by Raman spectroscopy. Further oxidation at higher i and CLR led to magnetite (Fe₃O₄) formation, while all other conditions led to increased DO and/or increased pH, with subsequent identification of only orange lepidocrocite (γ-FeOOH). GR showed the marginally higher NOM DOC and AMW fraction reductions. In synthetic water, differing operating parameters led to differences in φ and iron speciation, characterized by in-situ Raman spectroscopy, aqueous XRD, SEM, and cryo-TEM. High i in the presence of pitting promoters led to φ near unity where a GR intermediate was seen, and an end product of Fe₃O₄. A mechanism scheme summarizing EC speciation is proposed. A general model relating cell potential and current was developed for parallel plate continuous EC, relying only on geometric and tabulated variable inputs. For the model, the anode and cathode were vertically divided into n equipotential segments. Potential and energy balances were simultaneously solved for each vertical segment iteratively. Model results were in good agreement with experimental data, mean relative deviation was 9% for a low flow rate, narrow electrode gap, and polished electrodes.

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Development of a CFD-based model for the simulation of immobilized photocatalytic reactors for water treatment (2010)

A computational fluid dynamics (CFD) model for the simulation of immobilized photocatalytic reactors for water treatment was developed and evaluated experimentally. The model integrated hydrodynamics, species mass transport, chemical reaction kinetics, and irradiance distribution within the reactor. For the development of this integrated CFD model, each of the above phenomena was individually evaluated against experimental data and proper models were identified. The experimental evaluation was performed using various configurations of annular reactors and UV lamp sizes, over a wide range of hydrodynamic conditions (350
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Effects of UV/H₂O₂ advanced oxidation on physical and chemical characteristics of natural organic matter in raw drinking water sources (2009)

This thesis focused on the physical and chemical transformations undergone by natural organic matter (NOM) in two natural waters (from British Columbia, Canada) during ultraviolet plus hydrogen peroxide (UV/H₂O₂) advanced oxidation treatment as a function of UV fluence (up to 2000 mJ cm⁻­­­­­²­) and initial H₂O₂ concentration (up to 20 mg L⁻­­­­­­¹­). Under these conditions NOM was not mineralized but the hydroxyl radical (•OH) partially oxidized NOM leading to reductions in the chromophoric natural organic matter (CNOM) (i.e., NOM absorbing at 254 nm). NOM was degraded into more readily biodegradable compounds, such as aldehydes. An appreciable reduction in the very hydrophobic acid (VHA) fraction of NOM was observed. Considerable reductions in the formation potentials of trihalomethanes (THMs) or haloacetic acids (HAAs) were not observed. An increase in alkalinity slowed down the rate of degradation of CNOM during UV/H₂O₂. A dynamic kinetic model was developed to predict the degradation of CNOM. Model parameters were developed using isolated aquatic NOM from Suwannee River. For the two natural waters, the model adequately predicted the degradation of CNOM as a function of initial H₂O₂ concentration, irradiation time (i.e., UV fluence). Including the reduction in CNOM improved the modeling of H₂O₂ degradation, but H₂O₂ degradation was still slightly under predicted. For water that had undergone ultrafiltration (UF), NOM was readily mineralized during UV/H₂O₂ treatment due to the absence of high molecular size NOM. For water from which the VHA fraction of NOM was removed, UV/H₂O₂ treatment led to mineralisation of NOM suggesting that, when coupled with a pre-treatment capable of removing a large portion of the VHA fraction, UV/H₂O₂ can achieve reductions in TOC.Combining UV/H₂O₂ with downstream biological activated carbon (BAC) filtration led to reductions in NOM and formation potentials of THMs and HAAs. Formaldehyde and H₂O₂ were effectively removed by BAC.Development of a method for the determination of assimilable organic carbon (AOC) in UV/H₂O₂ treated water concluded that manganese dioxide was a suitable agent for the removal of H₂O₂ prior to AOC analysis. The method was applied to observe an increase in AOC as fluence increased during UV/H₂O₂ treatment of raw water.

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Master's Student Supervision (2010-2017)
Anion exchange resins for the removal of microcystins from surface water (2017)

Harmful algal blooms have markedly increased in frequency over the past two decades, due to rising global temperatures and chemical runoff produced by modern farming practices. Cyanobacteria, also known as the blue green algae, are an essential part of the aquatic food chain. Cyanobacterial toxins, which are released from the algal biomass, can contaminate drinking, recreational and agricultural water reserves. Such environmental and health hazards pose a serious threat to communities and many aquatic ecosystems. In particular, small, shallow lakes that are sources of drinking water for rural communities have been particularly affected by elevated levels of algal toxins. Conventional water treatment systems are inefficient in removing these toxins, and may produce hazardous by-products. Additionally, the effectiveness of chemical oxidants, like chlorine and ozone, is hindered by the presence of natural organic matter (NOM) and inorganic ions in the contaminated water. Such challenges reveal the need for alternative treatment technologies capable of removing algal toxins. Anionic ion exchange (IX) resins offer a promising and cost-effective treatment alternative for natural waters affected by high algal content and high dissolved organic carbon (DOC) levels. This research investigates the efficiency of strongly basic ion exchange resins for the removal of microcystin-LR (MCLR), the most common toxin released from the algal biomass, inorganic ions, and NOM from natural water sources. We focused specifically on optimizing resin dosage, resin regeneration, and scaling up such procedures for particular source waters. Our results showed that the resin exhibited an excellent adsorption capacity of 3850 µg/L, removing more than 80% of the MCLR within 10 minutes at examined resin dosages (10 to 1000 mg/L; 1mL of resin = 221 mg). Additionally, we examined the influence of operating parameters such as pH and adsorption capacity of the resin, as well as the impact of NOM fractions on the uptake of MCLR. The charge density and molecular weight of the source water NOM were found to play a major competitive role in the uptake of Microcystin-LR. The results of this study bring the promising potential of IX resins for the removal of Microcystins and NOM from surface waters to light.

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Degradation of cyanobacterial toxin microcystin-LR using UV/vacuum-UV advanced oxidation for drinking water treatment (2017)

Cyanobacterial blooms have been increasing in magnitude and frequency around the world and studies have concluded that climate change, population growth, and industrial development will accelerate this phenomenon. The presence of cyanobacterial blooms in drinking water sources is a concern due to the production of cyanobacterial toxins, which are known to damage internal organs and disrupt nervous system functions. Shallow surface water sources for small water systems are at a greater risk of eutrophication and small, remote communities often lack the resources and infrastructure for adequate treatment. In conventional water systems, instances of cyanobacterial blooms are typically addressed by chemical addition. However, many remote communities are difficult to access and are unable to maintain a consistent supply of chemical oxidants. This study investigated the capability of ultraviolet radiation at 254 nm and 185 nm wavelengths (UV/Vacuum-UV) to degrade microcystin-LR (MC-LR), one of the most commonly occurring and toxic cyanobacterial toxins. Results showed that substantial toxin removal could be achieved solely by direct photolysis with 254 nm. The addition of 185 nm increased MC-LR degradation through advanced oxidation by hydroxyl radicals (•OH). The presence of alkalinity and organic matter (DOC) reduced MC-LR degradation by scavenging •OH. DOC also absorbed 254 nm and 185 nm, requiring additional irradiation time to achieve a target UV dose. Chloride scavenged •OH, but in a reversible reaction, resulting in minimal impact on MC-LR degradation. The order of impact on MC-LR degradation by these common water constituents was DOC>Alkalinity>Chloride. In natural water with a complex matrix, MC-LR could be degraded from a typical concentration (15 µg/L) to below detection (
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Effect of UV-LED fluence rate and reflection on inactivation of microorganisms (2016)

Ultraviolet light emitting diodes (UV-LEDs) are emerging as viable alternative to traditional UV lamps for water disinfection. UV-LEDs possess many advantages, some of which include robust configuration, long lifetime, and small size. With UV-LED being an incipient technology, there are also a number of knowledge gaps and challenges towards their widespread applications to water disinfection. The research presented here focuses on addressing two such knowledge gaps; first, the impact of reflection from the reactor wall on the fluence rate distribution inside a UV-LED reactor, and second, the effect of UV fluence rate on the inactivation of microorganisms. Three UV-LEDs: 265nm, 275nm, and 285nm were utilized as the UV sources. The test microorganisms were E.coli ATCC 11229 and Fecal Coliform. Teflon (OD98), stainless steel and aluminum petri dishes were built and used as reflective materials. A new experimental method for evaluating the absorbed energy by a water sample during the UV-LED’s irradiation was proposed. This method was used to derive the E.coli kinetic models at wavelengths of interest. These kinetic models were useful for calculating the inactivation improvement due to reflection inside different reactors. At the same experimental condition, the E.coli log inactivation inside different reactors (reflective and non-reflective as control) was calculated and the kinetic models were utilized to back calculate the correspondent value for the UV fluence in the system. The ratio of the absorbed energy by the solution in a reflective material over that of the control experiment was reported as the improvement arising from reflection within the reactor. The maximum improvement in inactivation of E.coli was around 100% obtained in a reactor made of Teflon followed by nearly 60% and 30% increase in aluminum and stainless steel, respectively. The results also showed that the E.coli inactivation kinetics followed the time-dose reciprocity rule meaning that the same level of inactivation was observed for both high and low fluence rates; whereas the low fluence rate resulted in more Fecal Coliform inactivation than the high fluence rate at the same UV fluence. These observations were consistent for all three LEDs.

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UV/Vacuum-UV Advanced Oxidation Process for the treatment of micropollutants from drinking water sources under common operational temperatures (2016)

Vacuum-UV Advanced Oxidation Process (AOP) has been identified as a viable candidate to treat chemical contaminants in drinking water. In contrast to the commercially available and widely applied UV/H₂O₂ AOP, VUV AOP does not rely on the addition of chemicals for the generation of hydroxyl radicals. As a result, the technology is very appealing to small systems and rural communities which often lack infrastructure and qualified personnel to operate complex systems. The primary objective of this research was to investigate the effect of temperature on the removal efficiency and energy consumption of a UV/VUV flow-through photoreactor. Additionally, the optical absorption properties at 185 nm of water and naturally occurring solutes such as Natural Organic Matter (NOM), nitrate, sulphate and chloride were studied between 3.6 and 25.0 °C. The secondary objective of this research was to investigate the effect of UV/VUV treatment on the removal of a mixture of micropollutants (e.g., pharmaceuticals, hormones, pesticides). The results showed that temperature does not have a significant impact on process efficiency and energy consumption. Moreover, owing to the presence of naturally occurring solutes, it was found that the production of OH radicals was to some extent limited at 3.6 °C, therefore slightly lower removals were observed at low temperature. When evaluated on a mixture of micropollutants, the UV/VUV process could potentially degrade a variety of substances with feasible energy consumption. Other than for two of the 12 micropollutants tested, at a flow-rate of 1.9 L min-¹, the VUV process was competitive to the UV/H₂O₂ process.

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Water operator and community engagement to improve drinking water access in First Nations in British Columbia (2015)

Lack of access to safe drinking water is an issue disproportionately affecting First Nations in Canada and putting the health of First Nations communities at risk. Many First Nations in British Columbia are facing additional challenges for water treatment system design due to their small population and rural and remote location. Investing in infrastructure alone is not sufficient to ensure long-term water access and protection of community health. Water operators have been identified as key individuals to engage to ensure community appropriate water treatment solution design as well as long-term operation and maintenance of treatment systems. This work highlights the important role that water operators have both within their community and with external stakeholders involved in the design and management of treatment systems. It has also been identified that water operators are well placed to be educators in their community and be a trusted source of information for community members about their water. There is a need for increased support for operators from community leadership as well as more transparency and operator involvement in decision making, especially in relation to budgeting. Water operators reported serving their community as one of the main motivations in their work; however, it was also expressed that there was a lack of recognition and appreciation for their work from within their community. Increased community awareness about the importance of water operators is considered to be essential to increase operator support from their community. In turn, this support contributes to increased water operator job satisfaction and motivation, and ultimately water operator retention in communities. Community support for operators and the inclusion of operators in water related budgeting and decision-making is key to finding appropriate water treatment solutions and ensuring operators are able to provide communities with long-term access to safe drinking water.

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Plastic bags for water treatment : a new approach to solar disinfection of drinking water (2012)

Waterborne disease is the cause of death for over 1.6 million people annually, and it is contracted primarily through inadequate access to safe drinking water, inadequate sanitation facilities, and inadequate hygiene practices. Solar disinfection (SODIS) is a low-cost water treatment technology that uses resources that are commonly available in much of the developing world, the most important being plastic beverage bottles. SODIS relies on solar ultraviolet radiation to kill germs in contaminated water contained in these plastic bottles, so that water can be rendered safe for consumption. However, in remote regions plastic bottles are often unavailable, or are prohibitively expensive. For this reason there exists a need for an alternative to plastic bottles for SODIS use in remote regions of the world. In this study, real and artificial sunlight exposures, standard microbiological enumeration methods, and tensile strength and optical transmittance measurement methods, were used to evaluate whether a plastic SODIS bag is a potential alternative to SODIS bottles. SODIS bags were found to yield as much as 74% higher treatment efficiencies than SODIS bottles, which may be because the bags were able to reach the elevated temperatures that are shown to cause accelerated treatment. The physical wear of hanging SODIS was approximately half the rate (47%) of SODIS bags’ wear and this suggests that hanging SODIS bags may have a longer useful life. A curve relating water depth and the efficiency of the water treatment process in SODIS bags under certain representative treatment conditions was generated and used to predict the optimal geometry of SODIS bags. Additionally, a new method was proposed for calculating the solar UV dose, which may be more appropriate than conventional methods. These findings suggest that SODIS bags may be an appropriate alternative to SODIS bottles. The findings further provide information to guide the design and implementation of SODIS bags.

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Assimilable organic carbon formation during ultraviolet-hydrogen peroxide advanced oxidation treatment of surface water (2011)

Practice of UV/H₂O₂ advanced oxidation treatment has emerged as viable alternative for removing micro-pollutants and other organic contaminants from surface water. However, presence of natural organic matter (NOM) in water is problematic and hinders the efficacy of the treatment process. Indeed, NOM can undergo significant partial oxidation leading to generation of smaller more easily assimilable organic molecules (i.e., AOC). Earlier studies have found AOC as the potential cause of bacterial regrowth and other water health concerns thereof within the distribution system. Nonetheless, impact of UV/H₂O₂ process on biostability of downstream water has not gained much attention. However, a method recently developed by Hammes and Egli (2005) opened the opportunity for more accurate and relatively rapid quantification of the AOC. The main focus of this research was to modify and evaluate the protocol of Hammes and Egli (2005) for quantifying the biostability of water before and after UV/H₂O₂ process. More importantly, this research aimed to contribute substantially to the current understanding of easily assimilable organic molecules formation during UV/H₂O₂ treatment. As a result, different characterization techniques (e.g., HPSEC, UV₂₅₄, and TOC) were utilized to monitor transformation of NOM and to study the relationships among different NOM characteristics (e.g., molecular size distribution, UV₂₅₄, and AOC). Considering the concerns associated with NOM (especially when oxidation is applied in the treatment train), elimination of NOM ahead of the oxidation process can potentially increase the UV/H₂O₂ treatment efficacy as well as the finished water quality. Moreover, as the regulations become more stringent, many utilities hope to comply with them by retrofitting existing facilities and avoiding the construction of new ones. Thus, this research also focused to investigate the impact of a pre-treatment process such as coagulation to eliminate NOM prior to UV/H₂O₂ treatment. Using coagulation as pretreatment ahead of UV/H₂O₂ will be potentially of interest for those utilities that are currently applying coagulation and hope to comply with new regulations by minimum capital investment. More importantly, this would be beneficial because of the need to improve process efficacy and also final water quality and the reduced formation of disinfection by-products (DBPs) within the distribution system.

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